Allen-Bradley 1771-ASB Programmable Logic Controller Module

Allen-Bradley 1771-ASB Remote I/O Adapter Module is a PLC-5 era interface that enables PLC-2/3/5 control systems to communicate with distributed I/O through a 1771 Remote I/O subnet, acting as a slave device within the Universal I/O Chassis backplane and transferring data between the PLC-5 processor and remote I/O modules. It is designed to reside in a Universal I/O Chassis and receives power from the chassis backplane, not via an independent supply, reflecting its role as an integrated backplane device in the PLC-5 remote I/O architecture. Rockwell Automation lists the 1771-ASB as discontinued as of December 31, 2017, with the product no longer sold by the manufacturer, marking it as a legacy component for older PLC networks. On a single 1771 Remote I/O subnet, you can connect up to eight 1771-ASB adapters to extend remote I/O reach and interface multiple remote modules with the PLC-5 controller. Documentation from EPICS and Rockwell's literature reference the 1771-ASB as a Remote I/O Adapter Module used in PLC-2/3/5 networks, confirming its role in universal I/O backplanes within the 1771 family.